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What they are, how do they work and what are they used for?

I am pretty sure most of us have driven past a construction site and wondered what the various machines are used for. Some are humongous!
Those are the ones that require those traffic-slowing “abnormal loads” that we pass now and then on the highway. I always look at the machines being transported, and try to imagine what they do.
To solve a bit of the mystery for some of us, I have gone on a research mission to determine the names and uses of five construction machines that I think could be of interest.

 

Articulated Haulers

This type of machine is also known as an articulated dump truck (ADT), and is capable of traversing tough terrain.
These dump trucks are used for the removal of earth or construction rubble, among other types of materials, and have also been effective for snow removal. In an extreme situation, Linco Construction in Texas used their articulated haulers to evacuate victims of a Hurricane

 

 

 

 

 

Dragline Excavators

Dragline excavators are often used in road and underwater excavation, and in surface mining.
The heavier types of dragline excavators usually have to be assembled on site. These machines use a bucket and rope system to gather materials and dump them.

 

 

 

 

 

 

Sheepsfoot Rollers

The purpose of a sheepsfoot roller, which is also known as a tamping roller or padfoot roller, is used for soil compaction.
A typical sheepsfoot roller is made up of a drum with stud-like protrusions covering the surface of the drum. These studs can be manufactured in different sizes, depending on the type of soil that is to be compacted.

 

 

 

 

 

 

Cold planers

Cold planers are used to remove the surface of paved areas – a process known as milling. These milling machines grind the surface of, for example, a road (asphalt), in order to lay new asphalt, or to smooth out the road surface.
Milling allows for the road surface to be recycled, making it a positive factor in ongoing efforts to curb negative impacts on the environment.
Cold planers use a milling drum to cut the paved surface. Tool holders, which are attached around the drum, hold cutting tools which cut the pavement.
The milled materials are held in the machine’s scrapper, and then transferred from the cold planer, using a conveyor belt, to another vehicle to be transported from the site.

 

 

 

 

 

Tower Cranes

 

Cranes are often the first construction machines that we see, even when the site is not in plain sight – see what I did there 😉 These are very tall machines, which are used to lift various types of materials, in order to place them where they are required.
A typical tower crane consists of a base, mast, slewing unit, machinery arm, counter weights and an operator’s cab. The base of the crane is secured to a concrete pad, which provides support. The tower section (or mast) gives the crane height, and is connected to the base. The slewing unit houses the motor which allows the crane to rotate, and also includes a working arm (longer horizontal section), machinery arm (shorter horizontal section) and counter weights. The crane operator manoeuvres the crane from the operator’s cab.

 

 

 

 

During my research into this topic, I have enjoyed learning more about some of the machines that I have seen, but knew nothing about.

I do hope that next time you pass a construction site, and you see some of the machines that I have mentioned, that you will have a better understanding of their purpose.

 

Sources:
Babcock
Google
Wikipedia
Engineering Intro

 

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Under water construction

So whilst many of us think of underwater construction we think of it as a more modern building technique and we think of all the construction in Dubai, however in fact underwater construction actually dates as far back as to 23 BCE where Roman builders constructed the largest artificial harbour ever built in the open sea to date. Caeserea Maritima, where the remains can still be found.

We then have more modern examples of underwater construction like Lake Kariba where construction started in 1955 and was completed in 1959 and cost around 480 million USD.
We also have the world’s first underwater hotel built of the coast of Key Largo Florida which was actually a research facility dating back to the 1970’s La Chalupa Research Laboratory which has been converted into a hotel, named Under The Sea Lodge which opened it’s doors to guests in 1986. This building is completely underwater and is only accessible by scuba diving more than 6 meters down and gaining access via a “moon pool” which is located under the building.
We then have the mega structures in Dubai where they have taken underwater construction to new depths constructing islands and underwater hotels and water theme parks like The Palms and Atlantis.

So how does one actually build underwater?
Well you have to firstly create a stable and dry environment in which to build in order to work in the environment and place concrete in it.

We have basically two different methods / techniques in which to build underwater.
Firstly we have Cofferdams, which are temporary structures normally used where the construction area is larger and the water depth less, you also get different types of cofferdams.

• Earthen cofferdams,
• Doubled Cofferdams
• Rockfill Cofferdams
• Single walled Cofferdams
• Crib cofferdams
• Cellular cofferdams

Cofferdams are normally used for constructing bridge piers and other supporting structures

Then you get Caissons which are more permanent large hollow watertight structures which are used for repairing bridge foundations and dams.

You also get different type of caissons, namely:

• Box Caissons
• Open Caisson
• Suction Caisson
• Pneumatic Caisson

A good example of construction using Caissons is the Port of Ngquru just outside Port Elizabeth, which used 5 Caissons anchoring the ends of the breakwaters which required 18 000m³ of reinforced concrete.

So whilst there are different types of underwater construction it remains quite a complex and challenging construction method testing the boundaries of construction in general.

 

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Demolition

Demolition is the destruction, knocking down, pulling down, tearing down, flattening, razing, levelling, bulldozing, clearance, obliteration and annihilation of buildings and other man-made structures, however, it has been known that when one is stricken with immense hunger, one can demolish a whole pizza in one sweep.

Demolition contrasts with deconstruction, which involves taking a building apart while carefully preserving valuable elements for re-use purposes.

Demolition Plan:
For small buildings, such as houses, that are only two or three stories high, demolition is a rather simple process.
The building is pulled down either manually or mechanically using large hydraulic equipment: Elevated work platforms, Cranes, Bulldozers, Backhoe Loaders & Hydraulic Excavators.

 

Backhoe Loaders Basic workhorse machine that allows for multiple attachments. Short reach machines. Can work in moderately small areas

Hydraulic Excavators They provide for longer reach and power. A step up from the backhoe.

 

Larger buildings may require the use of a wrecking ball, a heavy weight on a cable that is swung by a crane into the side of the buildings. Wrecking balls are especially effective against masonry but are less easily controlled and often less efficient than other methods. Newer methods may use rotational hydraulic shears…

Used for cutting steel, cable and rebar and silenced rock-breakers attached to excavators to cut or break through wood, steel, and concrete. The use of shears is especially common when flame cutting would be dangerous.

For larger buildings or structures, however, it is imperative to make sure there is a plan in place. One thing about construction projects is that just as they went up, someday they must come down.

When that day arrives and the building has become unsafe or just seen better days, it’s time to call in the demolition experts.

First they need to assess your needs as there are many different factors involved in a building demolition and several different ways to go about it. Once your needs are determined, a plan is created. The plan will include how the demolition is to be carried out as well as all the equipment that will be used to do it. The ultimate goal is to get the building demolished in the safest and most efficient way possible. These decisions will depend on the size of the building, the building materials, the reason for the demolition and the location of the building.

Some methods that will be considered include:

1. Implosion

Large buildings like the World Trade Centre, tall chimneys, smokestacks, bridges, and increasingly some smaller structures may be destroyed by building implosion using explosives or terrorist trained pilots. Imploding a structure is very fast—the collapse itself only takes seconds—and an expert can ensure that the structure falls into its own footprint so as not to damage neighbouring structures. This is essential for tall structures in dense urban areas.

Any error can be disastrous, however, and some demolitions have failed, severely damaging neighboring structures. One significant danger is from flying debris, which, when improperly prepared for, can kill onlookers.

Another dangerous scenario is the partial failure of an attempted implosion. When a building fails to collapse completely the structure may be unstable, tilting at a dangerous angle, and filled with un-detonated but still primed explosives, making it difficult for workers to approach safely. A third danger comes from air overpressure that occurs during the implosion. Stephanie Kegley described shock waves by saying, “The shock wave is like a water hose. If you put your hand in front of the water as it comes out, it fans to all sides.” When cloud coverage is below 1,200 feet, it reacts like the hand in front of the hose. The wave from the shock fans out, instead of up toward the sky. If the sky is clear, the shock wave, a wave of energy and sound, travels upwards and disperses, but if cloud coverage is low, the shock wave can travel outwards, breaking windows or causing other damage to surrounding buildings.

Controlled implosion, being spectacular, is the method that the general public often thinks of when discussing demolition; however, it can be dangerous and is only used as a last resort when other methods are impractical or too costly

2. Deconstruction

A new approach to demolition is the deconstruction of a building with the goal of minimizing the amount of materials going to landfills. This “green” approach is applied by removing the materials by type material and segregating them for reuse or recycling. With proper planning this approach has resulted in landfill diversion rates that exceed 90% of an entire building and its contents in some cases. It also vastly reduces the CO2 emissions of the removing of a building in comparison to demolition.
Timber waste can be shredded using specialist timber shredders and composted, or used to form manufactured timber boards, such as MDF or chipboard.

3. Selective Demolition

This is used rather than flattening structures in one fell swoop which maximizes efficiency by reducing waste, repurposing reusable materials, and lessening environmental impact. This approach works hand in hand with Deconstruction.

Carrying out the plan
Once the plan is set, the demolition company will know the method, the equipment that’s necessary, the approximate cost, how much debris there will be, how it will be dispersed at the site and how long it will take to clean up. Back up plans and emergency plans will also be part of the overall demolition plan. After the plan has been finalised the company must get all necessary permits so they are safe when the demolition is carried out.

Like any job before the fun stuff begins there’s the preparation work that needs to be done and so site preparation is just as important as the demolition itself. The building must be completely cleaned out of the utilities like gas, water and electricity as well as the removal of hazardous materials.

After it’s all planned, legal aspects are covered and the site is ready, the demolition is scheduled and carried out. To some people seeing a building demolished is a thing of beauty.

The co-ordination and expertise that goes into pulling it off just right is truly staggering. In a lot of ways the building going down isn’t really an ending but a new beginning…

 

Sources:
https://en.wikipedia.org/wiki/Demolition
https://theconstructor.org/structures/demolition-methods-process-buildings-structures/13941/
https://en.wikipedia.org/wiki/Backhoe_loader
https://en.wikipedia.org/wiki/Excavator

 

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